P3.3.4 Detecting messages Flashcards
What is a carrier wave?
A wave that carries information
Which types of electromagnetic radiation can be used as carrier waves?
Radio waves, microwaves and infrared
Describe how the sound of a radio presenter travels from the microphone to your radio?
1) Microphone converts sound into an electrical signal 2) This signal is converted into a digital signal of 1s and 0s 3) Transmitter adds the digital signal to the carrier wave 4) This is modulation. The transmitter the changes the amplitude or frequency of the carrier wave. 5) Carrier wave is broadcast and travels across the country as a radio wave. 6) A radio set is tuned to the same frequency as the carrier wave. 7) Radio set converts the radio signal back into sound. 8) The loudspeaker plays the programme
Describe the difference between AM and FM
AM is amplitude modulation - it means changing the amplitude to represent 1s and 0s. FM is frequency modulation - it means changing the frequency of the carrier wave
What is modulation?
Changing the amplitude or frequency of a wave
What is diffraction?
Spreading out of waves around an obstacle or going through a gap
What is the connection between Hertz (Hz) and mega Hertz (MHz)?
1 MHz = 1 000 000 Hz
What is the connection between Hertz (Hz) and kilo Hertz (MHz)?
1 kHz = 1000 Hz
How can you calculate wavelength?
Wavelength = wave speed / frequency
What is an SI unit?
A unit that is used internationally to allow scientists all over the world to compare their data.
A radio wave is used to the find the position of an aircraft on a runway. It takes 0.000 002 seconds for the radio waves to travel from the control tower to the aircraft and back. Calculate how far away the aircraft is from the tower. Radio waves travel at 300 000 000 m/s
300 000 000 x 0.000 002 = 600m 600m / 2 = 300 metres
This method can be used to find distances to planets within our Solar System. Calculate the time it would take to receive a radio signal sent from Earth that reflects off Venus. Use the speed of radio waves above. The average distance to Venus = 108 000 000 000 m
2 x 108 000 000 000 = 216 000 000 000 m (there and back) Time = distance / speed 216 000 000 000 / 300 000 000 = 720 seconds
What is the connection between speed, distance and time?
Speed = distance/time
How can you calculate distance?
Distance = speed x time
How can you calculate time?
Time = distance / speed
Draw a diagram to show radio waves diffracting around hills towards a house.
